The present invention relates to a defrosting method and apparatus for a refrigerator, more particularly, to a defrosting method and apparatus for a refrigerator using a genetic algorithm (hereinafter, referred to as GA)-fuzzy theory.
The term, GA-fuzzy theory is a compound word of GA and the fuzzy theory. GA is an algorithm for continuously inferring an unknown correlative function suitable for a type of input data, to which a procedure of reproduction, hybridization or mutant in an ecosystem is applied. The fuzzy theory is for overcoming limitations of the crisp's logic consisting of `0` and `1`, and has been developed itself with variety. The pivot of the fuzzy theory is an inference method using a conditional function. The fuzzy inference method based on the modus ponens theory of Zadeh, a mathematician and founder of the fuzzy theory, infers an output for an input from the outside. Currently, there are widely used three kinds of fuzzy inference methods, that is, a direct inference method, an indirect inference method and a mixed inference method. Each inference method has an operation method for effecting an inference procedure of each inference method efficiently.
The direct inference method includes a max-min operation method and a max-dot operation method. The indirect inference method uses an operation method that a function belonging to a conclusion of each rule is included in an inferrer as a type of a monotonically increasing function. The mixed inference method uses an operation method that an objective function of the set rules are simplified to a linear equation or a constant value, thereby directly inferring by a numerical calculation method.
FIG. 1 is a perspective view roughly showing a structure of a common refrigerator. The right side of FIG. 1 represents the rear portion of the refrigerator. As shown in FIG. 1, there is provided a freezing room 2 and a cold-storage room 3 for storing food to the upper and the lower parts inside a body 1. Doors 2a and 3a are mounted to the front surface of body 1 for opening and shutting freezing room 2 and cold-storage room 3. An evaporator 4 is mounted to the lower end portion of freezing room 2 for heat-exchanging supplied air to cold air by the latent evaporation heat of the refrigerant. A fan 5 and a fan motor 5a are mounted to the right of evaporator 4 for circulating the cold air heat-exchanged by evaporator 4 to freezing room 2 and cold-storage room 3. A thermostatic damper 6 is mounted at the right side of the upper end portion of cold-storage room 3 for controlling amount of cold air provided into cold-storage room 3 by sensing a temperature of the inside of cold-storage room 3. Plural shelf members 7, which divide inner space, are mounted inside freezing room 2 and cold-storage room 3 for supporting food. Duct members 8 and 9 are mounted in the rear of freezing room 2 and cold-storage room 3 for controlling the flowing direction of the cold air so as to circulate the cold air heat-exchanged by evaporator 4 into freezing room 2 and cold-storage room 3. Also, cold air guiding paths 8a and 9a are formed beside the rear wall of freezing room 2 and cold-storage room 3 for guiding the cold air into freezing room 2 and cold-storage room 3. A compressor 10 is mounted to the rear lower end portion of body 1 for compressing a low-temperature and low-pressure gaseous refrigerant cooled in evaporator 4 into a high-temperature and high-pressure gaseous state. An evaporation dish 11 is mounted to the left side of compressor 10 for collecting the defrosting water (moisture in the air generated when the air supplied by driving fan 5a is cooled by heat-exchanging in evaporator 4). An auxiliary condenser 12 is mounted to the bottom of evaporation dish 11 for evaporating the defrosting water collected in evaporation dish 11. A main condenser 13 is embedded over the whole area of backboard 1a or the sidewalls of body 1 in the shape of zigzag for converting the high-temperature and high-pressure gaseous refrigerant compressed in compressor 10 into a low-temperature and high-pressure liquid refrigerant. A capillary tubing 14 is mounted to the one side of compressor 10 for reducing the pressure of the refrigerant liquidized in main condenser 13 up to the evaporation pressure to convert the refrigerant into a frostless low-temperature and low-pressure refrigerant. An antifrosting pipe 15 for preventing frosting phenomenon caused by the contact of the warm air outside and cold air inside body 1 is mounted to the lower front portion of body 1.
In the common refrigerator constituted as described above, its operation is as follows:
When power is supplied after setting a predetermined inner temperature, the temperature sensor mounted to a predetermined site of freezing room 2 judges whether the inner temperature excesses the set temperature or not. If the inner temperature of freezing room 2 is higher than the set temperature, compressor 10 and fan motor 5 drive, and at the same time, fan 5a starts to rotate. The refrigerant compressed to high-temperature and high-pressure gaseous state by compressor 10 evaporates the defrosting water collected in evaporation dish 11 as it passes through auxiliary condenser 12, and thereafter is cooled and liquidized to a low-temperature and high-pressure liquid refrigerant as it flows into main condenser 13. The liquid refrigerant prevents the frosting phenomenon in the refrigerator as it passes through antifrosting pipe 15, and reduces to the frostless low-temperature and low-pressure refrigerant to flow into evaporator 4 as it passes through capillary tubing 14 for expanding the liquid refrigerant up to the evaporation pressure.
FIG. 2 is a diagram showing a cold air flow of a common refrigerator. As shown in FIG. 2, air supplied when the low-temperature and low-pressure refrigerant pressure-reduced through capillary tubing 14 evaporates to gas while passing through several pipes is heat-exchanged to cold air in evaporator 4. And the low-temperature and low-pressure gaseous refrigerant cooled in evaporator 4 returns to compressor 10 so as to form a repeatedly circulating freezing cycle. The cold air heat-exchanged by evaporator 4 in FIG. 2 is guided along duct members 8 and 9 by the rotation of fan 5a according to driving of fan motor 5, and then is supplied into the inside of freezing room 2 and cold-storage room 3 via cold air guiding paths 8a and 9a. The temperature of the inside of freezing room 2 and cold-storage room 3 drops less than the set temperature due to the cold air.
FIG. 3 is a flow chart showing a conventional defrosting method of a refrigerator. As shown in FIG. 3, reference data with respect to the inner temperature of the evaporator and the operation time of the compressor are input, respectively. If the operation time of the compressor exceeds the reference data and the inner temperature of the evaporator drops less than the reference data, heater operates. If the inner temperature of the evaporator exceed the reference data after operating the heater, the heater stops operating. In the conventional defrosting method of a refrigerator as described above, input variables (e.g. the inner temperature of the evaporator or the operation time of the compressor) are measured, and directly compared with the reference data, thereby operating a defrosting heater. Therefore, the conventional defrosting method for a refrigerator has limitations on precision and accuracy in the case of an input function which has a many inflexion points and is impossible to differentiate because a microcomputer is programmed by using a crisp's logical algorithm consisting of `0` and `1`.